In the 3rd Generation Partnership Project (3GPP) that is a mobile communication system standardization project, introduction of device-to-device (D2D) communication into Release 12 as a new function is under consideration (see Non Patent Literature 1).
In the D2D communication, a plurality of nearby user terminals perform direct inter-terminal communication without passing through a network. On the other hand, in cellular communication that is normal communication of a mobile communication system, user terminals perform communication via a network.
The user terminal transmits and receives a discovery signal used for discovering a nearby user terminal in order to perform the D2D communication. After the discovery process, the user terminal performs the D2D communication with the nearby user terminal.